Lisa Mullen lectures MTT1

Question 1

4 things energy is required for

Answer 1

> motion (muscle contraction)
transport (of ions/molecules across membranes)
biosynthesis of essential metabolites
thermoregulation

Question 2

Why does Mg2+ deficiency make you feel tired

Answer 2

Mg2+ forms complex with ATP inside cells, deficiency impairs virtually all metabolism

Question 3

A) What class of enzyme transfers electrons

B)What class of enzyme transfers functional groups

Answer 3

A) oxidoreductases

B) transferases

Question 4

Which vitamin is needed for coenzyme:
A) FAD
B) NAD+

Answer 4

A) Riboflavin (B2)

B) Niacin

Question 5

Glycolysis:

A) which enzyme phophorylates glucose into glucose-6-phosphate

B) Which enzyme is involved in the committed step, and what is the reaction

Answer 5

A) Hexokinase

B) PFK-1 catalyses fructose-6-phosphate into fructose 1,6 bisphosphate

*both priming reactions

Question 6

Glycolysis:

Which reaction does Pyruvate kinase catalyse

Answer 6

phosphoenolpyruvate into pyruvate

Question 7

Inside the mitochondria, what is the link reaction

include the enzyme that catalyses it

Answer 7

pyruvate + CoA + NAD+ ——-> acetyl CoA + NADH + H+

catalysed by PDH complex

Question 8

Which 5 coenzymes make up PDH complex, and which 4 vitamins are vital for this complex

Answer 8

TPP, NAD+, CoA, FAD, Lipoic acid

Thiamine for TPP
Riboflavin for FAD
Niacin for NAD
Pantothenate for CoA

Question 9

What does ACIKSSFMO stand for (order of intermediates in TCA cycle)

Answer 9

Acetyl CoA
Citrate
Isocitrate
alpha-Ketoglutarate
Succinyl CoA
Succinate
Fumarate
L-Malate
Oxaloacetate

Question 10

What are the two shuttles used to regenerate NAD+ via transport of 2 electrons

Where is each one mainly found

How many moles of ATP is produced

Answer 10

1) glycerol-3-phosphate shuttle, in brain and muscle
2) malate-aspartate shuttle, in liver and heart
1. 5 or 2.5 moles ATP

Question 11

Which 4 complexes make up the ETC

Which soluble proteins link them

Answer 11

Complex I, II, III, IV

Linked by ubiquinone (coenzyme Q)
Cytochrome C (links III and IV)

Question 12

Name the antiporter protein that transports ADP3- into matrix in exchange for ATP4- out of matrix

Answer 12

adenosine nucleotide translocase

Question 13

Name of symporter that transports both phosphate and H+ into the matrix

Answer 13

phosphate translocase

Question 14

2 functional domains of ATP synthase

Answer 14

Fo: an oligomycin-sensitive proton channel
F1: an ATP synthase

Question 15

What is Atractyloside

Answer 15

found in thistle, specific inhibitor of adenosine nucleotide translocase

Question 16

The different subunits that comprise Fo and F1 domains of ATP synthase

Answer 16

Fo: 13-15 a, b and c subunits

F1: 9 subunits of alpha 3, beta 3, gamma, delta and reverse E

Question 17

2 uncoupling reagents that dissipate H+ gradient allowing H+ back into matrix via a diff route that is not ATP synthase, thus severing linnk between e- flow and ATP synthesis. Releasing energy as heat

Answer 17

occurs naturally: UCP1 (thermogenin): found in brown adipose tissue and has specific H+ chanel for H+ to flow back into matrix, releasing heat as it does so. Important in newborns to keep them warm

occurs unnaturally: DNP: a weight loss drug. A weak acid that crosses membranes ‘ferrying’ H+ across with it. Each DNP collects H+ from intemrembrane space, crosses inner membrane and deposits H+ in matrix. Can return to collect another proton

Question 18

Compare nuclear and mitochondrial genome

Answer 18

Nuclear:
Introns present
3% coding dna 
Histones associated
Maternal/paternal inheritance
20,000-30,000 genes encoded 

Mitochondrial genome:
no introns or histones
93% coding dna
Maternal inheritance only 
genes code for:
13 respiratory chain proteins
2 rRNA proteins
22 tRNA proteins (tRNA structure different)

Question 19

What are oxidative phosphorylation enzyme defects strongly associated with

Answer 19

alzheimers, parkinsons, type II diabetes

Question 20

heteroplasmy

Answer 20

presence of more than one type of mt DNA within a cell/ individual. It is important in determining the severity of diseases

Question 21

What is threshold effect

Answer 21

a disease will only present itself if 70% or more of mitochondria in a cell was mutant

Question 22

What does LHON stand for and what is it

Answer 22

Lebers hereditary optic neuropathy

single base change in mt gene ND4 (Arg>His) in complex I of ETC. Not enough ATP generated = damage to optic nerve = blindness

Question 23

What does MERRF stand for and what is it

Answer 23

Myoclonus epilepsy with ragged-red fibre

a point mutation in mt gene encoding tRNA specific for lysine, disrupts synthesis of proteins essential for OXPHOS = abnormal shaped mitochondria in skeletal muscle.

Ragged red fibres is red clumps of abnormal mitochondria that appears on staining

Question 24

What is MELAS syndrome, what does it stand for

>symptoms in childhood

Answer 24

Mitochondrial encephalomyopathy lactic acidosis

mt gene dysfunction effecting complex I and tRNA, effects brain and skeletal muscle

childhood symptoms: lactic acidosis, stroke-like symptoms with muscle weakness, seizures leading to loss of vision, involuntary muscle spasms (myoclonus), dementia

Question 25

What does KSS stand for and what is it | > symptoms

Answer 25

Kearns-sayre syndrome results from 5kb deletion of mt genome, onset before 20 symptoms: dementia, retinitis pigmentosa

Question 26

mt myopathies treatment options

Answer 26

occupational/ physical therapy: may extend range of muscle movement vitamin therapies: riboflavin, creatinine, CoQ, C, K and carnitine may help

Question 27

2 strategies to prevent mt myopathies

Answer 27

mitochondrial gene replacement (pronuclear stage) maternal spindle transfer

Question 28

glucose is polar, so how enters cells via glucose transport proteins (gluts) give 5 examples and where they are found

Answer 28

glut 1: found in erythrocytes, muscle, brain, kidney, colon, placenta glut 2: found in liver, pancreatic cells glut 3: found in brain glut 4: found in skeletal muscle, adipose tissue glut 5: small intestine (fructose transporter)

Question 29

Where does pentose phosphate pathway branch from two products of pentose phosphate pathway And what they’re used for

Answer 29

Branches from glycolysis at G-6-P Products: 1)ribose phosphate: used to synthesise RNA and DNA 2) NADPH: used for reductive biosynthesis and to maintain redox balance of cell

Question 30

what makes glycogen a GOOD energy store. What makes it a BAD energy store

Answer 30

GOOD: highly branched, large number of ends for phosphorylase and glycogen synthase to ensure rapid breakdown and resynthesis BAD: glucose is hydrophillic, it associates with water increasing overall weight and bulk

Question 31

2 mechanisms of glycogenolysis

Answer 31

1) glycogen phosphorylase breaks bonds between alpha1,4 linked glucose by addition of phosphate to produce glucose-1-phosphate 2) alpha1,6 bonds requires debranching enzyme alpha1,6 glucosidase which is a hydrolysis reaction producing free glucose

Question 32

allosteric regulation of glycogen phosphorylase in muscle

Answer 32

AMP activates phosphorylase as it is a sign of ATP depletion | ATP and gluc-6-phosphate inhibit phosphorylase as they are a sign of inc energy levels

Question 33

allosteric regulation of glycogen synthase

Answer 33

activated by gluc-6-phosphate and ATP In liver, glucose and G-6-P inhibits glycogenolysis

Question 34

How is glycogen phosphorylase activated by cAMP-dependent phosphorylation What effect does this cAMP cascade have on glycogen synthase

Answer 34

cAMP cascade leads to phosphorylation of serine in glycogen phosphorylase, this activates glycogen phosphorylase. It is in 'a' conformation opposite effect on glycogen synthase, it converts enzyme to 'b' conformation, the less active state

Question 35

what are main regulatory points for link reaction/ TCA cycle

Answer 35

link reaction: PDH complex | TCA cycle: citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase

Question 36

anaplerotic reactions of TCA cycle

Answer 36

pyruvate replenishes OAA via pyruvate carboxylase PEP replenishes OAA via PEP carboxylase Malate is replenished by pyruvate into malate via malic enzyme

Question 37

Names of complex I,II,III and IV in ETC

Answer 37

``` I = NADH dehydrogenase II = succinate dehydrogenase III = ubiquinone:cytochrome c oxidoreductase IV= cytochrome oxidase ```

Question 38

theory of rotational catalysis

Answer 38

conformation 1: ADP+Pi are bound conformation 2: ADP+Pi = ATP conformation 3: ATP released (active site has low affinity for ATP in this formation)

Question 39

What is mitochondrial genetic bottleneck

Answer 39

The randomness in the way mitochondria is inherited specifically in the oocyte amplification and maturation stage means we can’t predict outcome of mitochondrial inheritance

Question 39

Functions of liver

Answer 39

Glycogen synthesis Glycogenolysis Gluconeogenesis Fatty acid synthesis from glucose secrete as TAGs in VLDL Synthesise ketone bodies and secretes into blood as fuel for other tissues Stores fat soluble vitamins

Question 40

Why is brain most vulnerable to hypoglycaemia

Answer 40

1) cannot store glucose in significant amounts or synthesise glucose 2) cannot metabolise substrates other than glucose or ketone bodies 3) cannot extract sufficient glucose for their needs at low concentrations because glucose entry into brain is not facilitated by hormones

Question 41

Immediate and long term effects of insulin

Answer 41

Immediate: Inc rate of glucose uptake in muscle and adipocytes Modulation of activity of enzymes involved in glucose metabolism Long term: Inc expression of liver enzymes that synthesise glycogen Inc expression of adipocyte enzymes that synthesise TGs, this inhibits lipolysis in adipose tissue Functions as growth factor for some cells eg fibroblasts

Question 42

How is glycogen broken down in muscle vs liver

Answer 42

Muscle: glycogen >gluc 1 phosphate > gluc 6 phosphate > pyruvate > lactate +co2 Liver: glycogen >gluc 1 phosphate > gluc 6 phosphate > glucose via enzyme glucose 6 phosphatase

Question 43

How does glycogen form in first place | How do branches form

Answer 43

UDP-glucose donates first glucosyl residue and attaches it to aa tyrosine in protein glycogenin. Remaining glucose units added in alpha 1,4 linkage from UDP glucose creating growing chain Branching enzyme transfers block of 7 residues to growing chain to create new branch with alpha 1,6 linkage. New branch cannot form within 4 residues of existing branch